The reports of his death have not been officially confirmed. It will add to his family's anguish because the ungoverned status of large parts of Iraq makes it difficult to secure confirmation.

Image Caption:Mr Amin appeared with two other British-based men in an ISIS video

A statement from the Foreign and Commonwealth Office said: "We are aware of reports of the death of a British national in Iraq.

"We stand ready to talk to any family who may be affected.

"The UK is deeply concerned by the growth of terrorism in Iraq and Syria, which threatens the people in the entire region and the UK.

"The UK advises against all travel to Syria and much of Iraq and anyone travelling to these areas is exposing themselves to serious risk."

Image Caption:A woman walks past the scene of a bomb attack in Sadr City

In the Islamic State of Iraq and Syria (ISIS) video, posted to YouTube, Mr Amin appeared alongside students Nasser Muthana and Reyaad Khan - both 20 and from Cardiff. They urged Westerners to join the fighting in Iraq and Syria.

It comes as Iraqi forces were forced to withdraw from the northern city of Tikrit after meeting heavy resistance.

Government troops retreated to a base two and a half miles from the city after coming under heavy mortar and sniper fire.

Tikrit was captured by ISIS militants on June 12 and a push to retake it began at the beginning of July.